<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
    <link rel="stylesheet" href="bootstrap/css/bootstrap.min.css">
</head>
<body>
    <div class="container">
        <div class="btn-group dropup">
            <button type="button" class="btn btn-info">分裂式下拉菜单</button>
            <button type="button" class="btn btn-info dropdown-toggle" data-toggle="dropdown">
                <span class="caret"></span>
            </button>
            <ul class="dropdown-menu" role="menu">
                <li><a href="#">1</a></li>
                <li><a href="#">2</a></li>
                <li><a href="#">3</a></li>
                <li><a href="#">4</a></li>
            </ul>
        </div>

        <div class="btn-group">
            <button type="button" class="btn btn-info btn-lg">分裂式下拉菜单</button>
            <button type="button" class="btn btn-info dropdown-toggle btn-lg" data-toggle="dropdown">
                <span class="caret"></span>
            </button>
            <ul class="dropdown-menu" role="menu">
                <li><a href="#">1</a></li>
                <li><a href="#">2</a></li>
                <li><a href="#">3</a></li>
                <li><a href="#">4</a></li>
            </ul>
        </div>

        <div class="btn-group">
            <button type="button" class="btn btn-info">分裂式下拉菜单</button>
            <button type="button" class="btn btn-info dropdown-toggle" data-toggle="dropdown">
                <span class="caret"></span>
            </button>
            <ul class="dropdown-menu" role="menu">
                <li><a href="#">1</a></li>
                <li><a href="#">2</a></li>
                <li><a href="#">3</a></li>
                <li><a href="#">4</a></li>
            </ul>
        </div>

        <div class="btn-group">
            <button type="button" class="btn btn-info btn-sm">分裂式下拉菜单</button>
            <button type="button" class="btn btn-info dropdown-toggle btn-sm" data-toggle="dropdown">
                <span class="caret"></span>
            </button>
            <ul class="dropdown-menu" role="menu">
                <li><a href="#">1</a></li>
                <li><a href="#">2</a></li>
                <li><a href="#">3</a></li>
                <li><a href="#">4</a></li>
            </ul>
        </div>

        <div class="btn-group">
            <button type="button" class="btn btn-info btn-xs">分裂式下拉菜单</button>
            <button type="button" class="btn btn-info dropdown-toggle btn-xs" data-toggle="dropdown">
                <span class="caret"></span>
            </button>
            <ul class="dropdown-menu" role="menu">
                <li><a href="#">1</a></li>
                <li><a href="#">2</a></li>
                <li><a href="#">3</a></li>
                <li><a href="#">4</a></li>
            </ul>
        </div>
    </div>

    <script src="jquery/jquery-2.1.4.min.js"></script>
    <script src="bootstrap/js/bootstrap.min.js"></script>
</body>
</html>